프로그래머스 해시 완주하지 못한 선수

import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;

class Solution {
    public String solution(String[] participant, String[] completion) {
		HashMap<String, Integer> map = new HashMap<>();
		for (int i = 0; i < participant.length; i++) {
			map.put(participant[i], map.getOrDefault(participant[i], 0)+1);
		}
		for (int i = 0; i < completion.length; i++) {
			map.put(completion[i], map.get(completion[i])-1);
			if(map.get(completion[i]) == 0)
				map.remove(completion[i]);
		}
		Set<String> set = map.keySet();
		Iterator<String> ite = set.iterator();
		String answer = ite.next();
		return answer;
	}
}